Commonly known in the art are heat exchangers used in connection with an automotive vehicle for cooling the engine of the vehicle. The heat exchanger generally comprises upper and lower manifolds providing fluid reservoirs and a plurality of coolant or fluid tubes extending between the manifolds providing fluid communication therebetween.
Liquid coolant may pass through the upper and lower manifolds in a liquid to air heat exchanger because liquid passes through the tanks and tubes while air is passed external and between the tubes for cooling the fluid contained therein.
There are also air to air heat exchangers wherein air is passed within the tubes and air is passed externally thereover for heat exchange. This type of heat exchanger may be used in turbo charged engines wherein heat exchangers are routinely used for cooling compressed "charged" air from a turbo charger on route to the cylinders for combustion.
The components of the heat exchanger are generally welded or soldered together. The core, comprising the fluid tubes, fins and side support members, receives ambient cooling air passing through and around the cooling fins and is disbursed about the cooling tubes, thereby allowing the fluid to release the majority of its thermal energy. The high amount of energy released causes large thermal expansion of the coolant tubes, cooling fins and header. However, the side support members are generally at a lower temperature since the heated fluid does not flow directly therethrough. This large thermal expansion of part of the core causes stresses between the tanks and fluid tubes and side members. Significant stresses caused from the differences in the thermal expansion of the members over time can cause cracking and fatigue between the joints. This may result in leaks, lost pressure, and the engine lost horsepower output. It is therefore desirable to reduce stresses while allowing normal expansion to continue.
U.S. Pat. No. 5,257,662, issued Nov. 2, 1993 in the name of Osborn illustrates a typical heat exchanger assembly including a pair of manifolds with headers and a core member connected between the headers. The core member commonly includes a plurality of fluid tubes extending between the manifolds to provide fluid communicating therebetween, a plurality of fins connected to the fluid tubes for enhancing heat exchange, and structural side members connected between the manifolds at the outer sides of the core member.
Heat exchangers commonly use the solid, structural side members and do not address the problem of thermal expansion, and therefore cause stresses on the joints and result in cracking and fatigue thereof.
Another type of heat exchanger is illustrated in U.S. Pat. No. 3,034,770, issued May 15, 1962 in the name of Hiersch. This type of heat exchanger includes a pair of manifolds with a core therebetween. The core comprises a pair of parallel rigid side wall structures interconnecting the manifolds. The side wall structures include a plurality of longitudinal inlet warm-up passages and a plurality of by-pass passages. The warm-up passages openly connect the inlet in one manifold to the by-pass passages of the first and second manifolds. Between the side wall structures is the core comprising a plurality of fluid tubes openly connecting the first manifold to the second manifold. The inlet and outlet are preferably adapted for connection to an oil system under pressure. The oil entering the inlet passes through the intake passage and the warm-up passages to the second manifold. When the oil is cold, the thermal static valve is adapted to open the by-pass passages so that the passages will pass the cold oil from the second manifold directly to the first manifold outlet. When the oil is warm, the thermal static valve is adapted to close the by-pass passage so that oil passes from the second manifold through the core passages in typical heat exchanger manner. Therefore, the patent utilizes the outside passages only when the oil is cool, and thereafter the outside passages are shut off during normal fluid flow and heat exchanger process.